Vehicle disk brake lining wear

ABSTRACT

An abrasion detecting apparatus for a friction member comprises a detecting switch having facing electric contacts constituted on the one hand as a rotating member such as the brake disk and on the other hand a lead wire embedded in a friction member such as a brake pad facing the rotating member. The switch is interposed in a circuit having an indicating device such as a lamp connected to an electric source. The portion of the lead wire embedded in the friction member is covered over the entire surface thereof with an insulating layer such as an insulating tube.

United States Patent Sakata et al.

[4 1 Mar. 14, 1972 [54] VEHICLE DISK BRAKE LINING WEAR [72] Inventors:Mamoru Sakata; Hiroyulri Komori, both of Tokyo; Katsuhiko Fuiii,Fukuoka- Machi, all of Japan [21] Appl. No.: 52,930

[30] Foreign Application Priority Data July 23, 1969 Japan ..44/69978[56] References Cited UNITED STATES PATENTS 1,902,759 3/1933 Cataudella..340/52 A UX Madison ..340/52 A UX Puma ..340/52 A X 3,223,795 12/1965Yerman.... 340/52 A UX 3,271,737 9/1966 Bezemek... ..340/52 A 3,45 6,2367/ 1969 Labartino et al. ..340/52 A 3,553,642 1/1971 Rike et a1 ..340/52A Primary Examiner-Alvin H. Waring Attorney-Waters, Roditi, Schwartz &Nissen [57] ABSTRACT An abrasion detecting apparatus for a frictionmember comprises a detecting switch having facing electric contactsconstituted on the one hand as a rotating member such as the brake diskand on the other hand a lead wire embedded in a friction member such asa brake pad facing the rotating member. The switch is interposed in acircuit having an indicating device such as a lamp connected to anelectric source. The portion of the lead wire embedded in the frictionmember is covered over the entire surface thereof with an insulatinglayer such as an insulating tube.

6 Claims, 4 Drawing Figures VEHICLE DISK BRAKE LINING WEAR BRIEF SUMMARYOF THE INVENTION The invention relates to apparatus for detecting wearin a friction member. The friction member may be a brake pad in a diskbrake, a brake shoe in drum brakes, a clutch shoe in a friction clutch,or the like.

The apparatus according to the invention includes means for detectingwhen a predetermined wear or abrasion in the friction member hasoccurred and to signal the time for replacement of the friction member.

According to the invention there is provided abrasion detectingapparatus comprising first and second frictionally engageable members,one member being of abradable material, and detection means fordetecting and indicating abrasion of said one member beyond apredetermined amount and (including switch means) inclusive on the onehand the other of said members and on the other hand a lead wireembedded in said one member, and insulation means covering said leadwire in entirety at least in the portion thereof embedded in said onemember.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view, partly insection, of one embodiment according to this invention,

FIG. 2 is a sectional view taken along line Il-II in FIG. 1,

FIG. 3 is a sectional view similar to FIG. 2 of a modified embodiment ofthe invention, and

FIG. 4 is a sectional view showing an arrangement according to the priorart.

DETAILED DESCRIPTION This invention relates to an apparatus which, whenan abrasion ofa friction member such as a brake pad in a disk brake, abrake shoe in a shoe brake, a clutch shoe in a friction clutch or thelike has reached a predetermined limit, detects it and thereby noticesthe time for replacement of such a member.

In the known apparatus as shown in FIG. 4 a lead wire b is embedded in afriction member a and the wire b and a rotating member, such as a brakedisk facing the member a, are constructed as electrical contacts facingone another for forming a detection switch, so that when the twocontacts are brought into contact with another in the course of theabrasion of the friction member a. that is when the lead wire b isexposed in the course of the abrasion of the friction member a andthereby is brought into mechanical and electrical contact with thefacing rotating member, an electrical circuit for a detecting device isclosed so that the device is operated by flow of electric current. It isusual in this conventional arrangement that the lead wire b embedded inthe friction member a is bare in entirety or is partly bare at least atits end c as shown in FIG. 4, for example, as a result of cutting acovered electric wire. Additionally, the friction member a containslarge quantities of a good electrical conducting material such as ironpowder, aluminum powder or the like. Accordingly, it has been found fromthe results of the inventors research that, often, when the memberbecomes wet from rain water or the like, the wet portion becomes anelectrical conductor to produce an electric current flow between the twocontacts. Hence, even if the friction member a is not yet abraded, thedetecting switch operates as if the same were closed, so that anelectric current flows through the detecting circuit to operate thedetecting device.

The invention has been developed in consideration of this, and accordingto this invention there is provided an apparatus of the type in which adetecting switch 4 is formed having mutually facing electrical contactscomprising a rotating member I such as a brake disk or the like and alead wire 3 embedded in a friction member 2 such as a brake pad or thelike facing the rotating member I. As seen in FIG. 1, the lead wire 3 iselongated and extends linearly, in parallel relation to member I, fromthe periphery of member 2 to the region of the center thereof. Theswitch 4 is interposed in a connecting circuit including a detectingdevice 5 such as a lamp and an electric source 6. In accordance with theinvention, at least that portion of lead wire 3 embedded in the frictionmember 2 is covered throughout the entire surface thereof with aninsulating layer 7 such as an insulating tube.

As the means for the entire surface covering, it can be considered, forinstance, that the insulating layer 7 around the periphery of the leadwire 3 is closed at its end as if it were formed into a baglike shape asshown in FIG. 2 or that the end thereof is not closed but a conventionaltype of lead wire 3 with the insulating layer 7 is bent back on itselfso that the end thereof projects out of the friction member 2 as shownin FIG. 3.

According to the arrangement as shown in FIG. 3, it is only necessarythat a long lead wire, only the peripheral surface of which has beenpreviously insulation-covered, is cut in succession, so as to beadvantageous for mass production. Numeral 8 denotes a protection tubeapplied to cover the projecting part of the lead wire 3.

The drawing illustrates the case where the invention is applied to adisk brake. In this case, the friction member 2 constitutes a brake pad,and a pair of the pads are arranged so as to face the opposite surfacesof a brake disk comprising the rotating member 1, and the constructionis such that the members 2 are actuated by an oil pressure pistoncylinder 9 provided on one side thereof. Numeral I0 denotes an oil inletopening and numeral 1] denotes a hand operated switch interposed in thedetection circuit.

According to this invention, at least that portion of the lead wire 3which is embedded in the friction member 2 is covered throughout theentire surface thereof with the insulating layer 7, so that even when,for example, the friction member 2 becomes wet with rain water or thelike, there will never be any accidental current flow, that is, anyaccidental operation of the detecting device, and thus the arrangementis effective in preventing any erroneous operation and it is simple inconstruction and low in manufacturing cost.

What is claimed is:

l. Abrasion detecting apparatus for a disk brake assembly constitutedbya rotatable disk member and an abradable friction member facing the diskmember and applicable thereagainst to develop friction and slow therotatable disk member, said detecting apparatus comprising an elongatelead wire embedded in said friction member and extending linearly insubstantially parallel relation to said disk member, said lead wireextending inwardly from the periphery of the disk member to the regionof the center of the friction member, and insulation means covering saidlead wire in entirety in the portion thereof embedded in the frictionmember.

2. Abrasion detecting apparatus as claimed in claim I wherein saidinsulation means comprises an insulating envelope of tubular shapecompletely enclosing the embedded portion of the lead wire in said onemember.

3. Abrasion detecting apparatus as claimed in claim 1 wherein saidinsulation means comprises an insulation layer on said lead wire, saidwire having an exposed end, said wire being folded onto itself so thatsaid exposed end extends outside said one member and the remainder ofthe wire embedded in said one member is completely covered by saidlayer.

4. Abrasion detecting apparatus as claimed in claim 3 comprising aninsulation tube on said one member enclosing the lead wire where itprojects from said one member to cover said exposed end. I

5. Abrasion detecting apparatus as claimed in claim 3 wherein said wireis constituted of a subdivided length of wire with the insulation layerthereon.

6. Abrasion detecting apparatus as claimed in claim 1 comprising aninsulation tube on said one member enclosing the lead wire where itprojects from said one member.

1. Abrasion detecting apparatus for a disk brake assembly constituted bya rotatable disk member and an abradable friction member facing the diskmember and applicable thereagainst to develop friction and slow therotatable disk member, said detecting apparatus comprising an elongatelead wire embedded in said friction member and extending linearly insubstantially parallel relation to said disk member, said lead wireextending inwardly from the periphery of the disk member to the regionof the center of the friction member, and insulation means covering saidleAd wire in entirety in the portion thereof embedded in the frictionmember.
 2. Abrasion detecting apparatus as claimed in claim 1 whereinsaid insulation means comprises an insulating envelope of tubular shapecompletely enclosing the embedded portion of the lead wire in said onemember.
 3. Abrasion detecting apparatus as claimed in claim 1 whereinsaid insulation means comprises an insulation layer on said lead wire,said wire having an exposed end, said wire being folded onto itself sothat said exposed end extends outside said one member and the remainderof the wire embedded in said one member is completely covered by saidlayer.
 4. Abrasion detecting apparatus as claimed in claim 3 comprisingan insulation tube on said one member enclosing the lead wire where itprojects from said one member to cover said exposed end.
 5. Abrasiondetecting apparatus as claimed in claim 3 wherein said wire isconstituted of a subdivided length of wire with the insulation layerthereon.
 6. Abrasion detecting apparatus as claimed in claim 1comprising an insulation tube on said one member enclosing the lead wirewhere it projects from said one member.